Haskell错误 - "缺少附带绑定"

Question

我有以下haskell代码处理添加多项式:

module PolyLA2 where  -- defines the module name so you can import from another haskell file

type Coeff = Int
type Exp = Int
type Polynomial = [(Coeff, Exp)] -- a list of terms in a polynomial formula

addpoly::Polynomial -> Polynomial -> Polynomial
addPoly [] ys = ys -- Base case 
addPoly xs [] = xs -- Base case 
addPoly ((a,b):xs) ((c,d):ys)
     | a == c = ((a, b + d) : (addPoly xs ys))
     | a < c = ((a,b) : (addPoly xs ((c,d) : ys)))
     | a > c = ((c,d) : (addPoly ((a,b) : xs) ys)) 

我相信逻辑是正确的,但是,当我尝试编译它时,我得到"缺少伴随绑定错误"我的问题是什么导致此错误？

Answer 1

这条线:

addpoly::Polynomial -> Polynomial -> Polynomial

应该:

addPoly::Polynomial -> Polynomial -> Polynomial

注意这封信P.